1. Field of the Invention
The present invention relates to a thin film magnetic head and a method of manufacturing the same, and more particularly to a combination type thin film magnetic head constructed by stacking an inductive type writing thin film magnetic head and a magnetoresistive type reading thin film magnetic head.
2. Description of the Related Art
Recently a surface recording density of a hard disc device has been improved, and it has been required to develop a thin film magnetic head having an improved performance accordingly. A combination type thin film magnetic head is constructed by stacking an inductive type thin film magnetic head intended for writing and a magnetoresistive type thin film magnetic head intended for reading on a substrate, and has been practically used. In general, as a reading magnetoresistive element, an element utilizing anisotropic magnetoresistive (AMR) effect has been used so far, but there has been further developed a GMR reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than that of the normal anisotropic magnetoresistive effect by several times.
In the present specification, elements exhibiting a magneto-resistive effect such as AMR and GMR reproducing elements are termed as a magnetoresistive reproducing element or MR reproducing element.
By using the AMR reproducing element, a very high surface recording density of several gigabits/inch2 has been realized, and a surface recording density can be further increased by using the GMR element. By increasing a surface recording density in this manner, it is possible to realize a hard disc device which has a very large storage capacity of more than 10 gigabytes.
A height (MR Height: MRH) of a magnetoresistive reproducing element is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. The MR height MRH is a distance measured from an air bearing surface on which one edge of the magnetoresistive reproducing element is exposed to the other edge of the element remote from the air bearing surface. During a manufacturing process of the magnetic head, a desired MR height MRH can be obtained by controlling an amount of polishing the air bearing surface.
At the same time, the performance of the recording magnetic head is also required to be improved in accordance with the improvement of the performance of the reproducing magnetic head. In order to increase a surface recording density, it is necessary to make a track density on a magnetic record medium as high as possible. For this purpose, a width of a write gap at the air bearing surface has to be reduced to a value within a range from several micron meters to several sub-micron meters. In order to satisfy such a requirement, the semiconductor manufacturing process has been adopted for manufacturing the thin film magnetic head.
One of factors determining the performance of the inductive type thin film writing magnetic head is a throat height TH. This throat height TH is a distance of a pole portion measured from the air bearing surface to an edge of an insulating layer which serves to separate a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible. The reduction of this throat height is also decided by an amount of polishing the air bearing surface.
Therefore, in order to improve the performance of the combination type thin film magnetic head having the writing inductive type thin film magnetic head and reading magnetoresistive type thin film magnetic head stacked one on the other, it is important that the recording inductive type thin film magnetic head and reproducing magnetoresistive type thin film magnetic head are formed with a good balance.
FIGS. 1-9 show successive steps for manufacturing a conventional standard thin film magnetic head, in these drawings A depicts a cross-sectional view of a substantial portion of the head and B represent a cross sectional view of a pole portion. Moreover, FIGS. 10-12 are a cross sectional view of a substantial portion of the completed thin film magnetic head, a cross sectional view of the pole portion, and a plan view of the substantial portion of the thin film magnetic head, respectively. It should be noted that the thin film magnetic head is of a combination type in which the inductive type thin film magnetic head for writing is stacked on the reproducing MR element.
First of all, as shown in FIG. 1, an insulating layer 2 consisting of, for example alumina (Al2O3) is deposited on a substance 1 made of a non-magnetic and electrically insulating material such as AlTiC and having a thickness of about 5-10 xcexcm.
Next, as shown in FIG. 2, a bottom shield magnetic layer 3 which protects the MR reproduction element of the reproducing head from the influence of an external magnetic field, is formed with a thickness of 3 xcexcm.
Afterwards, as shown in FIG. 3, after depositing an insulating layer 4 of thickness 100-150 nm serving as a shield gap layer by sputtering alumina, a magnetoresistive layer 5 made of a material having the magnetoresistive effect and constituting the MR reproduction element is formed on the shield gap layer with a thickness of several tens nano meters and is then shaped into a given pattern by the highly precise mask alignment.
Then, as shown in the FIG. 4, an insulating layer 6 is formed such that the magnetoresistive layer 5 is embedded within the insulating layers 4 and 6.
Next, as shown in the FIG. 5, a magnetic layer 7 made of a permalloy is formed with a film thickness of 3 xcexcm. This magnetic layer 7 has not only the function of the upper shield layer which magnetically shields the MR reproduction element together with the above described bottom shield layer 3, but also has the function of one of poles of the writing thin film magnetic head. Here, the magnetic layer 7 is called a first magnetic layer by taking into account the latter function.
Then, after forming a write gap layer 8 made of a non-magnetic material such as alumina and having a thickness of about 200 nm on the first magnetic layer 7, a second magnetic layer 9 made of a material having a high saturation magnetic flux density such as permalloy (Ni:50 wt %, Fe:50 wt %) and nitride iron (FeN) is formed with a desired shape by the highly precise mask alignment. The second magnetic layer 9 having formed into a given pattern is called a pole chip, and a track width is determined by a width W of the pole chip. Therefore, in order to realize a high surface recording density, it is necessary to decrease the width W.
In this case, a dummy pattern 9xe2x80x2 for coupling the bottom pole (first magnetic layer) with the top pole (third magnetic layer) is formed simultaneously. Then, a through-hole can be easily formed by polishing or chemical mechanical polishing (CMP).
In order to prevent an effective width of writing track from being widened, that is, in order to prevent a magnetic flux from being spread at the bottom pole upon the data writing, portions of the gap layer 8 and bottom pole (first magnetic layer) 7 are etched by an ion beam etching such as ion milling. The structure after this process is shown in FIG. 5. This structure is called a trim structure and this portion serves as a pole portion of the first magnetic layer.
Next, as shown in FIG. 6, after forming an insulating layer, for example alumina film 10 with a thickness of about 3 xcexcm, the whole surface is flattened by, for instance CMP.
Subsequently, after forming an electrically insulating photoresist layer 11 into a given pattern by the mask alignment of high precision, a first layer thin film coil 12 made of, for instance a copper is formed on the photoresist layer 11.
Continuously, as shown in FIG. 7, after forming an electrically insulating photoresist layer 13 on the thin film coil 12 by the highly precise mask alignment, the photoresist layer is sintered at a temperature of, for example 250-300xc2x0 C.
In addition, as shown in FIG. 8, a second layer thin film coil 14 is formed on the flattened surface of the photoresist layer 13. Next, after forming a photoresist layer 15 on the second layer thin film coil 14 with the highly precise mask alignment, the photoresist layer is flattened by performing the sintering process at a temperature of, for example 250xc2x0 C.
As described above, the reason why the photoresist layers 11, 13 and 15 are formed by the highly precise mask alignment process, is that the throat height TH and MR height MRH are defined on the basis of a position of the edges of the photoresist layers on a side of the pole portion.
Next, as shown in FIG. 9, a third magnetic layer 16 made of, for example a permalloy and having a thickness of 3 xcexcm is selectively formed on the second magnetic layer (pole chip) 9 and photoresist layers 11, 13 and 15 in accordance with a desired pattern. This third magnetic layer 16 is coupled with the first magnetic layer 7 at a rear position remote from the pole portion through the dummy pattern 9xe2x80x2, and the thin film coil 12, 14 passes through a closed magnetic circuit composed of the first magnetic layer and the second and third magnetic layers.
Furthermore, an overcoat layer 17 made of alumina is deposited on the exposed surface of the third magnetic layer 16. Finally, a side surface of an assembly at which the magnetoresistive layer 5 and gap layer 8 are formed is polished to form an air bearing surface (ABS) 18 which is to be opposed to the magnetic record medium. During the formation of the air bearing surface 18, the magnetoresistive layer 5 is also polished to obtain a MR reproducing element 19. In this way, the above described throat height TH and the MR height MRH are determined. This condition is shown in FIG. 10. In an actual thin film magnetic head, electric conductors and contact pads for performing the electrical connection to the thin film coils 12, 14 and MR reproduction element 19 are formed, but they are not shown in the drawings.
As shown in FIG. 10, an angle xcex8 (apex angle) between a line S connecting side corners of the photoresist layers 11,13,15 for isolating the thin film coils 12,14 and the upper surface of the third magnetic layers 16 is an important factor for determining the performance of the thin film magnetic head together with the above described throat height TH and MR height.
Moreover, as shown in the plan view of FIG. 12, the width W of the second magnetic layer 9 and a pole portion 20 of the third magnetic layer 16 is small. Since the width of the track recorded on the magnetic record medium is defined by this width W, it is necessary to narrow this width as small as possible in order to achieve a high surface recording density. It should be noted that in this figure, for the sake of convenience, the thin film coils 12, 14 are shown concentrically.
In the method of manufacturing the conventional thin film magnetic head, there is a problem that after forming the thin film coil, the top pole could not be formed precisely on the protruded coil section covered with the insulating photoresist especially along the inclined surface (apex). That is to say, in the known method, the third magnetic layer is formed by first plating a magnetic material such as permalloy on the mountain shaped coil with a height of about 7-10 xcexcm, by applying the photoresist with a thickness of 3-4 xcexcm, and by shaping the magnetic layer into a given pattern by means of the photolithography technology.
Now it is assumed that the photoresist formed on the protruded coil portion into a given pattern should have a thickness of 3 xcexcm or more, a thickness of the photoresist at a bottom or root of the inclined portion would amount to about 8-10 xcexcm.
On the one hand, the top pole formed on the protruded coil portion having a height of about 10 xcexcm as well as on the write gap layer formed on the flat surface should have a narrow portion in the vicinity of the edges of the insulating photoresist layers (for instance layers 11 and 13 in FIG. 7) in order to realize a narrow track width. Therefore, it is necessary to form the pattern having a width of 1 xcexcm by using the photoresist film having a large thickness of 8-10 xcexcm.
However, it is extremely difficult to form the photoresist film having a thickness of 8-10 xcexcm into a pattern having a width of about 1 xcexcm, because upon the light exposure in the photolithography, a pattern deformation might occur due to reflection of light and resolution is reduced due to the thick photoresist layer. In this manner, it is extremely difficult to form a top pole defining precisely a narrow track width by patterning.
Then, as is shown in the above explained conventional thin film magnetic head, in order to write data by means of the pole chip capable of forming the narrow track width, after forming the pole chip, the top pole is formed to be connected to the pole chip. In other words, in order to solve the above problem, a divided structure is adopted, that is, the pole chip for determining the track width and the third magnetic layer for introducing the magnetic flux.
However, the known thin film magnetic head, particularly the recording head formed as in the above manner still has the following problems.
(1) The throat height TH and MR height MRH are determined by taking a position of the edge of the insulating layer isolating the thin film coil on a side of the pole portion as a reference position, but the insulating layer is usually made of an electrically insulating organic photoresist layer and is liable to be deformed by heat. During the formation of the thin film coil, the insulating layer might be deformed by the heating treatment at about 250xc2x0 C., and a pattern size of the insulating layer changes, and the throat height TH and MR height MRH might be deviated from desired design values. As explained above, the photoresist layer has a very large thickness at this portion, and thus the influence due to the deviation of pattern is also large.
(2) In the above mentioned combination type thin film magnetic head, it is important to attain a good balance between the writing thin film magnetic head and the reading MR element. However, in the conventional combination type thin film magnetic head, for instance when the air bearing surface 18 is polished such that the throat height TH can be formed to a desired design value, the MR height MRH of the MR reproducing element might be also changed, and when the air bearing surface is polished to obtain the MR height MRH having a desired design value, the throat height TH might be deviated from a desired value in this manner, it is difficult to provide a combination type thin film magnetic head having desired characteristics.
(3) In the known method of manufacturing the combination type thin film magnetic head, since the throat height TH of the writing thin film magnetic head and the MR height MRH of the reading MR element have a fixed relationship, there is another problem that it could not respond quickly to various needs of users. That is to say, if it is required to provide a combination type thin film magnetic head, in which a MR height MRH is identical with that of the so far manufactured heads, but a throat height TH is smaller than that of the so far manufactured heads, or if it is required to provide a combination type thin film magnetic head, in which a MR height MRH is smaller than that of the so far manufactured heads although a throat height TH is equal to that of the so far manufactured heads, such requirements could not be fulfilled only by adjusting a polishing amount of the air bearing surface. Therefore, the manufacturing process has to be reviewed from the beginning, and thus such a request could be responded quickly.
(4) Since the pole chip and top pole are contacted with each other via a small contact area, and they are brought into contact with each other at right angles, the magnetic flux is liable to be saturated at the contact portion, and therefore a satisfactorily high writing characteristic could not be obtained.
(5) Since a positional relation between the pole chip and the top pole is determined by the alignment of the photoresist layer, a center line of the pole chip viewed from the air bearing surface might deviate largely from a center line of the top pole. Then, the data writing might be carried out by means of the magnetic flux leaked from the top pole, and the effective track width might be increased and data might be erroneously recorded on an adjacent track.
It is an object of the present invention to provide a thin film magnetic head, in which the above mentioned various problems can be solved advantageously, a pattern size of an insulating layer constituting a reference position with respect to an air bearing surface is not deviated by a heating treatment during the formation of a thin film coil, and therefore a throat height TH having a desired design value can be attained stably.
It is another object of the invention to provide a thin film magnetic head, in which a contact area between a pole chip and a top pole can be effectively increased to completely or substantially completely avoid a saturation of a magnetic flux at a pole portion.
It is another object of the invention to provide a thin film magnetic head, in which an increase in an effective track width and a decrease in a manufacturing yield can be avoided.
It is another object of the invention to provide a method of manufacturing such thin film magnetic heads having excellent characteristics in an efficient and accurate manner.
It is another object of the invention to provide a method of manufacturing a combination type thin film magnetic head, in which a pattern of an insulating layer defining a positional reference with respect to an air bearing surface is not deviated by a heating treatment during the formation of a thin film coil to obtain the throat height TH, apex angle xcex8 and MR height MRH having desired design values, and the throat height TH and MR height MRH can be controlled independently from each other, while a good balanced condition between the throat height and the MR height is not destroyed so that users"" requests for these heights can be satisfied promptly.
According to a first aspect of the invention, a thin film magnetic head comprises:
a first magnetic layer having a pole portion;
a second magnetic layer having a pole portion which is to be opposed to a magnetic record medium and defines a width of record tracks, and an end surface which constitutes an air bearing surface together with an end surface of said pole portion of said first magnetic layer;
a third magnetic layer which is brought into contact with said second magnetic layer on a side opposite to said first magnetic layer and is magnetically coupled with said first magnetic layer at a portion remote from said air bearing surface;
a gap layer made of a non-magnetic material and being interposed between the pole portion of the first magnetic layer and the pole portion of the second magnetic layer at least at the air bearing surface;
a thin film coil having a portion which is arranged between said first magnetic layer and said second and third magnetic layers with interposing an insulating layer therebetween to generate a writing magnetic flux for the magnetic record medium; and
a substrate which supports said first, second and third magnetic layers, gap layer, insulating layer and thin film coil;
wherein said second magnetic layer is extended up to a rear region beyond said pole portion to form an extended rear portion which is brought into contact with the third magnetic layer, and a part of said first magnetic layer except for at least said pole portion and the thin film coil isolated by said insulating layer are embedded within a recessed portion formed in the substrate.
In a preferable embodiment of the thin film magnetic head according to the first aspect of the invention, a width of the rear portion of said second magnetic layer is larger than that of the pole portion of the second magnetic layer constituting the pole chip. In this case, a width of the rear portion may be gradually increased. This expanded angle of the rear portion of the second magnetic layer is preferably set to 30-180xc2x0.
Moreover, in a preferable embodiment of the thin film magnetic head according to the first aspect of the invention, said second magnetic layer is made of a material having a high saturation magnetic flux density such as a permalloy.
Furthermore, a portion of the first magnetic layer which is opposed to the pole portion of the second magnetic layer via the gap layer may preferably be protruded toward the second magnetic layer, and a width of the protruded portion is substantially equal to a width of the pole portion of the second magnetic layer. The protruded structure of the first magnetic layer may be preferably formed by etching, while the pole portion of the second magnetic layer is used as a mask.
In another preferable embodiment of the thin film magnetic head according to the first aspect of the present invention, the thin film magnetic head is constructed as a combination type thin film magnetic head by arranging a magnetoresistive type reproducing element for reading on a surface of the third magnetic layer opposite to the surface which is brought into contact with said second magnetic layer such that an end surface of the reproducing element is exposed on the air bearing surface.
According to a second aspect of the invention, a method of manufacturing a thin film magnetic comprises:
the step of forming a recessed portion in a surface of a substrate;
the step of forming a first insulating layer on the surface of the substrate including a surface of the recessed portion;
the step of forming a first magnetic layer having a pole portion on at least a part of the surface of the substrate on which said first insulating layer is formed;
the step of forming a thin film coil within the recessed portion such that the thin film coil is isolated by a second insulating layer;
the step of forming a gap layer on at least said pole portion of the first magnetic layer as well as on a surface of said second insulating layer after making said first magnetic layer and second insulating layer to have a coplanar surface;
the step of forming a second magnetic layer on said gap layer such that the second magnetic layer extends over the pole portion of the first magnetic layer as well as over a rear region beyond the pole portion;
the step of forming a third magnetic layer such that the third magnetic layer is brought into contact with the second magnetic layer and is brought into contact with said first magnetic layer at a rear portion remote from an air bearing surface; and
the step of forming the air bearing surface to be opposed to a magnetic record medium by polishing said substrate, pole portions of said first and second magnetic layers and gap layer sandwiched by these pole portions while an edge of the recessed portion formed in the substrate is used as a positional reference.
In a preferable embodiment of the method of manufacturing the thin film magnetic head according to this second aspect of the invention, upon forming said second magnetic layer, a width of the rear portion thereof beyond the pole portion is gradually increased. In this case, this expanded angle may be preferably set to 30-180xc2x0.
In another preferable embodiment of the method of manufacturing the thin film magnetic head according to the second aspect of the invention, after forming said second magnetic layer, the pole portion of said first magnetic layer is etched while the pole portion of the second magnetic layer is used as a mask. This etching may be carried out such that a part of a thickness of the first magnetic layer is removed or may be conducted to remove the first magnetic layer over its whole thickness.
Moreover, in another preferable embodiment of the method of manufacturing a thin film magnetic head according to the second aspect of the invention, said step of forming the recessed portion in the surface of the substrate comprises:
the step of forming a photoresist layer selectively on a part of the surface of the substrate at which the recessed portion is to be formed;
the step of forming a metal or metal compound layer constituting a mask by a plating, while said photoresist layer is used as a mask;
the step of forming a mask by removing said photoresist layer, said mask having an opening corresponding to the recessed portion to be formed; and
the step of forming the recessed portion in the surface of the substrate by a reactive ion etching through the opening.
In this case, the reactive ion etching may be conducted by using, as a reactive gas, a fluorine series gas such as CF4 and SF6 or a chlorine series gas such as BCl3 and Cl2 or one of these gas diluted with an oxygen or an inert gas.
Before forming the mask made of metal or metal compound, an insulating layer may be formed on the substrate. Then, after forming the recessed portion by the etching, said mask made of metal or metal compound may be removed by etching while said insulating layer is used as an etching stopper. It is a matter of course that said mask made of metal or metal compound may be remained.
The reactive ion etching can form the deep recessed portion having a depth not less than 5 xcexcm in an accurate manner. In this case, an inclination angle of a side wall of the recessed portion may be preferably set to 45-75xc2x0, particularly 55-65xc2x0. It should be noted that the thus formed recessed portion has a highly smooth inner wall.
In another preferable embodiment of the method of manufacturing the thin film magnetic head according to the second aspect of the present invention, a magnetoresistive type reproducing element for reading is formed on said third magnetic layer such that the reproducing element is electrically isolated and magnetically shielded to construct the thin film magnetic head as a combination type thin film magnetic head.
Upon manufacturing such a combination type thin film magnetic head, before forming the first magnetic layer, a first shield layer for effecting a magnetic shield on the substrate, a magnetoresistive material layer is formed such that this layer is embedded within an insulating layer, then said first magnetic layer which also serves as a second shield is formed, and during the polishing process for forming the air bearing surface, said first shield layer as well as said magnetoresistive material layer are polished to form the magnetoresistive type reproducing element whose end surface is exposed on the air bearing surface.
Furthermore, according to a third aspect of the invention, a method of manufacturing a combination type thin film magnetic head having an inductive type writing thin film magnetic head and a magnetoresistive type reading thin film magnetic head for reading successively stacked on a substrate comprises:
the step of forming a recessed portion in a surface of a substrate;
the step of forming a first insulating layer on an inner surface of the recessed portion as well as on a part of the surface of the substrate;
the step of forming a first magnetic layer on a surface of said first insulating layer;
the step of forming a thin film coil within the recessed portion such that the thin film coil is isolated by a second insulating layer;
the step of forming a gap layer made of a non-magnetic material on surfaces of said first magnetic layer and second insulating layer;
the step of forming a second magnetic-layer on a surface of said gap layer such that the second magnetic layer is opposed to a pole portion of the first magnetic layer and is brought into contact with said first magnetic layer at a portion remote from an air bearing surface;
the step of forming a reading magnetoresistive layer on a surface of said second magnetic layer such that the magnetoresistive layer is embedded within a shield gap layer in an electrically isolated and magnetically shielded manner;
the step of forming a third magnetic layer on said shield gap layer; and
the step of forming the air bearing surface to be opposed to a magnetic record medium by polishing said substrate, pole portions of said first and second magnetic layers, gap layer sandwiched by these pole portions, shield gap layer, magnetoresistive layer and third magnetic layer, while an edge of the recessed portion formed in the substrate is used as a positional reference;
wherein a throat height of the inductive type thin film writing magnetic head is adjusted independently from a MR height of the magnetoresistive type reading thin film magnetic head by controlling a thickness of said first insulating layer.
According to a fourth aspect of the present invention, a method of manufacturing a combination type thin film magnetic head having an inductive type writing thin film magnetic head and a magnetoresistive type reading thin film magnetic head for reading stacked on a substrate comprises:
the step of forming a recessed portion in a surface of a substrate;
the step of forming a first insulating layer on an inner surface of the recessed portion as well as on a part of the surface of the substrate;
the step of forming a first magnetic layer on said first insulating layer;
the step of forming a thin film coil within the recessed portion such that the thin film coil is isolated by a second insulating layer;
the step of forming a gap layer made of a non-magnetic material on said first magnetic layer and second insulating layer;
the step of forming a second magnetic layer on said gap layer, said second magnetic layer having a pole portion which is opposed to a pole portion of the first magnetic layer and a rear portion which extends beyond the pole portion;
the step of forming a third magnetic layer which is brought into contact with said second magnetic layer as well as with said first magnetic layer at a portion remote from an air bearing surface;
the step of forming a reading magnetoresistive layer on said second magnetic layer such that the magnetoresistive layer is embedded within a shield gap layer in an electrically isolated and magnetically shielded manner;
the step of forming a fourth magnetic layer on said shield gap layer; and
the step of forming the air bearing surface to be opposed to a magnetic record medium by polishing said substrate, first, second and second magnetic layers, gap layer, shield gap layer, magnetoresistive layer and fourth magnetic layer, while an edge of the recessed portion formed in the substrate is used as a positional reference;
wherein a throat height of the inductive type thin film writing magnetic head is adjusted independently from a MR height of the magnetoresistive type reading thin film magnetic head by controlling a thickness of said first insulating layer.
Further, according to a fifth aspect of the invention, a method of manufacturing a combination type thin film magnetic head having an inductive type writing thin film magnetic head and a magnetoresistive type reading thin film magnetic head for reading stacked on a substrate comprises:
the step of forming a first magnetic layer on a surface of a substrate in accordance with a given pattern;
the step of forming a recessed portion in the surface of the substrate, while said first magnetic layer is used as a mask;
the step of forming a first insulating layer on an inner surface of the recessed portion;
the step of forming a reading magnetoresistive layer on said first magnetic layer such that the magnetoresistive layer is embedded within a shield gap layer;
the step of forming a second magnetic layer on said first insulating layer within said recessed portion as well as on said shield gap layer;
the step of forming a thin film coil on said second magnetic layer within the recessed portion such that the thin film coil is isolated by a second insulating layer;
the step of forming a gap layer made of a non-magnetic material on said second magnetic layer and second insulating layer;
the step of forming a third magnetic layer which is opposed to said second magnetic layer via said gap layer and is brought into contact with said second magnetic layer at a portion remote from an air bearing surface; and
the step of forming the air bearing surface to be opposed to a magnetic record medium by polishing said substrate, first magnetic layer, shield gap layer, second magnetic layer, gap layer and third magnetic layer, while an edge of the recessed portion formed in the substrate is used as a positional reference;
wherein a throat height of the inductive type thin film writing magnetic head is adjusted independently from a MR height of the magnetoresistive type reading thin film magnetic head by controlling a thickness of said first insulating layer.
In the methods according to the above mentioned third to fifth aspects of the present invention, the throat height can be controlled independently from the MR height by adjusting a thickness of the first insulating layer formed within the recessed portion. For instance, even when the air bearing surface is polished such that the MR height becomes constant, the throat height can be adjusted by controlling a thickness of the first insulating layer. In this manner, the throat height can be formed to have a desired design value without loosing a good balanced condition between the throat height and the MR height. Moreover, since a thickness of the first insulating layer can be controlled very simply, various needs of users can be satisfied in a prompt manner. By controlling a thickness of the first insulating layer within a range of 0.2-0.8 xcexcm, it is possible to adjust the throat height within a substantially same range.
Furthermore, the apex angle is defined by an inclination angle of the side wall of the recessed portion, and this angle is not varied by the high temperature process for photoresist layers. Therefore, it is possible to obtain the apex angle having a desired design value.
In case of forming the recessed portion in the substrate, it is preferable to conduct the reactive ion etching through the metal or metal compound mask. By using the reactive ion etching, the deep recessed portion having a depth not less than 5 xcexcm, an inclination angle of a side wall of the recessed portion of 45-75xc2x0, particularly 55-65xc2x0, and a highly smoothed inner surface can be formed in an accurate and efficient manner.
The reactive ion etching for forming the recessed portion may be conducted by using, as a reactive gas, a fluorine series gas such as CF4 and SF6 or a chlorine series gas such as BCl3 and Cl2 or one of these gases diluted with an oxygen or inert gas.
Furthermore, before forming the mask made of metal or metal compound, an insulating layer may be formed on the substrate. Then, after forming the recessed portion by the etching, said mask made of metal or metal compound may be removed by etching while said insulating layer is used as an etching stopper. It should be noted that said mask made of metal or metal compound may be remained as in the methods according to the fourth and fifth aspects of the present invention.
Moreover, in the method according to the above mentioned fourth aspect of the present invention, upon forming said second magnetic layer, a width of the rear portion beyond the pole portion may be widened than the pole portion. In this case, it is preferable that the rear portion of the second magnetic layer is gradually increased with an expansion angle of 30-180xc2x0.
Also in the methods according to the third to fifth aspects of the invention, after forming the second magnetic layer, the pole portion of the first magnetic layer may be etched to constitute the trim structure while the pole portion of said second magnetic layer is used as a mask.